Seems like this thread has wandered a bit... the original question was a "like kind" replacement for a blown SX-200. In that the Wesleyg hasn't provided more info on the version being replaced (could be anything from an old analog 216 up to an EL/ML), I think Lightninghorse offered the most to the point answer on that one.
As for sourcing of systems and parts, I'd like to toss in my two cents. Fred at Resale has been the most consistently supportive secondary vendor I've ever dealt with. If you walk into his shop, you'll see every Mitel system from the SX-20 through the ICP mounted on their test benches. If it's Mitel, Fred can support it for you.
Even though their pricing is as good as you can find, their level of service is even more important. Three years ago, a hotel customer's analog power supply blew out late on a Saturday night. At that point I didn't have a spare in inventory but when I called Fred, he got out of bed, drove to his shop and put a replacement PS out on his loading dock for me to pick up. By early Sunday morning, my hotel customer was back in business. I got to be a hero because I had a good vendor behind me.
